Wild populations of the iconic Mekong giant catfish will be driven to extinction if hydropower dams planned for the Mekong River go ahead, says a new report by WWF.

The report, River
of Giants: Giant Fish of the Mekong, profiles four giant fish
living in the Mekong that rank within the top 10 largest freshwater fish
on the planet.

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At half the length of a bus and weighing up to 600kgs, the Mekong River's giant freshwater stingray (Dasyatis laosensis) is the world's largest freshwater fish. The critically endangered and culturally fabled Mekong giant catfish (Pangasianodon gigas) ranks third at up to 3 metres in length and 350kgs.

Dam will present unsurmountable barrier for giant fish

"A fish the size of a Mekong giant catfish, simply will not be able to swim across a large barrier like a dam to reach its spawning grounds upstream," said Roger Mollot, Freshwater Biologist for WWF-Laos. "This would lead to the collapse of the wild population of this iconic species."

Current scientific information suggests the Mekong giant catfish migrate from the Tonle Sap Lake in Cambodia up the Mekong River to spawn in northern Thailand and Laos. Any dam built on the lower Mekong River mainstream will block this migration route.

The hydropower dam planned on the Mekong River at Sayabouly Province, northern Laos, is a threat to the survival of the wild population of Mekong giant catfish. The Sayabouly Dam is the first lower Mekong River mainstream dam to enter a critical stage of assessment before member countries of the Mekong River Commission advise on whether to approve its construction.